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Greywater
The domestic or household wastewater that comes from the laundry and bathroom is called 'greywater'. Toilet water is termed 'blackwater' and although kitchen water is technically termed greywater, it is treated as blackwater.
Recycling household greywater for use on garden beds is an excellent way of saving water and saving money! Unlike rainwater, which is seasonally available, greywater is available every time you shower or wash. The average house creates up to 83,000 litres of greywater per year.
Using greywater in the garden
Greywater is suitable for irrigating most garden areas including ornamental beds and lawns. Even native gardens can thrive with greywater, simply alter the type of detergent that you use to one that is low or has no phosphorus.
It is important to note that there has not been a lot of research done into the long-term effects of greywater application to plant and soil health. We recommended you continually check on the plants and the soil being irrigated with the greywater. If you do notice any negative effects on the soil or the plants, change the watering regime or rest the area from grey water use for a period of time until the plants return to a higher level of vitality. A common problem of greywater use is overwatering!
Will a system work at my house?
There are several ways to set up a greywater system, which may depend on the amount of 'drop' from the greywater origin to the garden bed. Systems can be as simple as a flow diversion fitting and hose, or something more complex such as a holding tank and pump with underground agipipe irrigation.
Are there components of greywater that can affect my garden?
As a general rule it is best to avoid irrigating gardens when the following are in your greywater:
Washing detergents with high phosphorous levels (many brands now have low or nil phosphorous, so choose one of these)
Bleaches and other disinfectants
Fats (from soaps)
Washing detergents using salt. Many cheaper brands use salt as a filler. It does not add to the washing power of the powder. Use only concentrates; or, better still, liquid detergents.
For a comprehensive list of detergents and the levels of salt and phosphorus that each contains please visit www.lanfaxlabs.com.au.
Are there any health issues related to greywater use?
Again, there are situations where greywater can contain organisms that may pose health concerns, however this can be avoided by following these points:
Don't use nappy-wash water in greywater
Don't allow children to play with or in the greywater
Don't allow pets to drink the greywater
Use subsurface distribution such as porous hoses or drippers beneath a layer of mulch -that is, do not spray greywater into the air
If irrigating edible plants, don't use on plants that are consumed raw or undercooked. Preferably don't use it on food crops at all. Fruit trees can be irrigated with grey water but the water must be kept at the root zone and not sprayed onto the foliage or fruit.
If holding tanks are used, don't store unused greywater for longer than 24 hours and remember to keep filters on tanks free of lint. Tanks must be cleaned out regularly to remove sludge build-up
Plumbing regulations state that drainage and water supply work must be carried out by a licensed plumber. This includes plumbing greywater overflow back into the sewage system. Refer to the EPA in your state and your local council for laws governing the use of greywater in your area.
Simple diverter systems
The simplest way to get greywater onto the garden is by diverting the water directly from the laundry or bathroom. There are a number of products available on the market that range in price depending on their complexity.
Funnel inserts
One of the simplest products, the black rubber funnel is ideal for situations where the water does not need to be diverted away quickly such as from a bath. This style of device does not need to be installed by a plumber and is easily removed when not required. Simply unscrew your wastewater inspection cap and insert the funnel.
This system is prone to backflow due to the narrow opening on the black funnel. To avoid flooding, thoroughly test this option by remaining present while it is active.
In-line diverter
In line diverters are designed to cut into the existing wastewater piping from the bathroom or laundry. Most systems rely on a valve that allows the water to either be diverted onto the garden or continue on down to the sewage.
Make sure that the water from toilets or the kitchen are not able to flow into the diverter, check the location of all piping prior to installing the diverter.
Other Collection Options
There are various greywater tank systems, as shown here, including the effective Bulleen Art & Garden Nursery garbage bin conversion (legal in Victoria, but check with local authorities in other states).
Dispersing the water
All piping must remain below the height of the diverter and must also be able to be dispersed from the system as quickly as it enters, so that the water will not flow straight back into the house.
Greywater must be dispersed under mulch. It's important that there are no airborne particle as this could pose a health risk from bacteria in the greywater.
Do not allow your greywater to run off your property.
Check with the environmental protection authority or water authorities in your state for further information.
Diverters incorporating surge tanks
Using a surge tank in a greywater system allows water to be slowed and cooled before it reaches the garden. Backflow problems are far less common as an overflow on the surge tank sends any excess water down the sewer rather than back into the house.
Water distribution is more consistent over the entire length of area irrigated. Decreasing the speed in which the water travels to the garden helps to minimise water runoff and prevents mulch and soil from washing away.
The Surge tank
Water from the bathroom or laundry enters the top of the surge tank via a pipe no smaller in diameter than that coming out of the house. Located at the base of the tank is the pipe that carries the water to the garden. An overflow from the tank is located at the top of the tank that flows back into the sewer, this pipe should be the same diameter as the inlet pipe.
A tank size between 30 and 100 litres is normally adequate as a surge tank for the majority of applications.
Greywater cannot be stored for any longer than 24 hours, always ensure that all water has drained completely from the tank at the end of each cycle.
Dispersing the water
The water is best distributed in pipes laid between the soil and mulch layer, piping options include drainage (agi.) pipe, standard poly pipe with holes drilled and dripline. The choice of piping depends on the size of the filter used. PLEASE NOTE that the picture to the right is to demostrate the type of piping that can be used. The pipe MUST be laid sub-surface (ie. covered by either soil or mulch).
The finer the filter, the more maintenance required, systems with filters and low water emitting drippers are more likely to get clogged by hair and lint. Where possible try not to use filters at all.
Pumped Greywater systems
Pumped greywater systems allow the water to be pumped from a lower to a higher section of the property. This is necessary when the garden is located above the height of the house. Pumped systems usually include some type surge tank where the pump is located and require power to operate.
Pumped systems require electricity, a licensed electrician may be necessary to install an outdoor electrical outlet. Pumped systems normally require a number of filters that require maintenance to prevent foreign objects from blocking the pump.
Dispersing the water
All pumped wastewater must be dispersed underground. A hose connected to the pump is normally placed at the highest end of the garden bed to be watered. The hose is inserted into 50 mm drainage (agi) pipe located between the mulch and soil surface running down the length of the bed. Moving the hose between garden beds every 2-3 days ensures even watering across the entire property.
Installation
Please note that many greywater systems require a licenced plumber to install them.
Rebates
Many Australian Water Authorities have introduced a rebate system for rainwater tanks, greywater systems, irrigation systems and mulches. Click here for a list of Australian Water Links.
An Update - February 2007
The use of greywater in gardens has grown exponentially in the last year as the drought and water restrictions force gardeners to take a more active approach to keeping their gardens alive. Unfortunately, incorrect information on how to use greywater in the garden has appeared in newspapers and on radio gardening programs, and ill-informed home gardeners are making some terrible mistakes. Click here to read the latest greywater research results.
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The information contained on this page is Copyright © SGA and intended for personal use only.
You may not use the information for any other purpose without the express written permission of SGA.
